Engine coolant formulations generally consist of a major amount of a coolant liquid such as ethylene glycol or water and a minor amount of other components like silicates, phosphates, nitrates, borates, molybdates, organic acids, and azoles. Generally, these other components are present in the coolant liquid as salts because the formulation is generally in the pH range of 7 or higher, up to 14. To the extent the engine contains ferrous metals which contact the formulation, a formulation pH greater than 7 facilitates protective film formation on the ferrous metal surface. It should also be noted that a component group such as the borates including borax (Na2B4O5 (OH)4.8H2O), which can exhibit an acidic pH at low water levels, but forms an alkaline buffer solution as the water content increases, would similarly be useful.
Identified by function, the additives introducible into the engine coolant formulations include but are not limited to deposit control materials, scale inhibitors, corrosion inhibitors, dyes, defoamers, bitterants, surfactants, freeze point depressants, and biocides.
Some of these components are solids that must be dissolved such as in the major amount of coolant liquid. Some of these components contribute to corrosion inhibition when in a finalized engine coolant formulation. The corrosion inhibiting components are incorporated to prevent pitting and other forms of corrosion that can dramatically shorten the operating life of an engine. While the major amount of coolant liquid can typically be inexpensively obtained close to the sites where engine coolant formulations are prepared from various commercial sources, and can be simply incorporated into the formulation, the minor components generally require more specialized production techniques or production in large volumes in relatively few commercial facilities in order to be economically produced for eventual use in the formulation. Thus, the production of engine coolant formulations with corrosion inhibiting components tends to be centralized in a few locations, with the completed formulations then being shipped long distances to sites where they are put into use. This shipping of large volumes of liquid formulations can add significantly to the cost of the final product.
In many engine coolant formulations, the major amount of coolant liquid is ethylene glycol. Ethylene glycol functions as a freeze point depressant and can be harmful when ingested in sufficient quantities. Nonetheless, engine coolant formulations do not always require the incorporation of a freeze point depressant such as ethylene glycol. For example, the ethylene glycol component would not be needed in marine engines that are constantly running or in engines used in tropical environments. In those instances, the major amount of liquid may be water, which is readily available and non-toxic. In other instances, such as in arctic conditions, the freeze point depressant qualities of ethylene glycol or a liquid alcohol freeze point depressant is an absolute requirement.
In addition, safety considerations related to freeze point depressants like ethylene glycol make shipping engine coolants containing this material difficult and costly, in addition to the cost associated with shipping this volume of material. It is thus desirable to lower both the risk associated with the use of materials like ethylene glycol, as well as the shipping cost associated with the volume of material being transported.